1. Field of the Invention
This invention relates to the fabrication of a thin-film magnetic head. In particular, it relates to a method of fabricating a stitched writer portion of such a head that is suitable for high data-rate encoding of magnetic information.
2. Discussion of the Related Art
Thin film magnetic heads are used to encode and decode data stored in the form of small magnetized regions on disks and tapes. These heads contain a read portion, which is typically a shielded magnetic field sensor of a giant magneto-resistive (GMR) type, and a write portion, consisting of a magnetic pole and yoke structure inductively energized by current carrying coils.
The need to encode and decode data stored with increasing areal densities and at increasingly higher data rates has necessitated the design of very narrow write heads with high linear resolution. The narrow write head allows data to be stored in narrow tracks, the high linear resolution, requiring narrow write gaps and strong magnetic fields, allows the storage of more data per unit length of track.
The need to produce narrow heads, narrow gaps and complex topologies has led to several novel fabrication schemes. Chen et al (U.S. Pat. No. 5,283,942) teach a method for fabricating a planar thin film head wherein a sacrificial layer is introduced to provide greater control over the gap planarization procedure. Ju et al (U.S. Pat. No. 5,375,023) teach a method for fabricating a thin film inductive head having staggered pole tips and a self-aligned recording gap region. Tong et al (U.S. Pat. No. 5,726,841) teach a method for forming a trimmed-head pole tip with beveled surfaces that is capable of recording data with narrow track widths. Rottmayer (U.S. Pat. No. 5,446,613) teaches a method for forming a head that combines a read portion and a write portion and whose poles themselves carry high current with minimal heating and low current density. Dill et al (U.S. Pat. No. 5,898,548) teaches a method for forming a magnetic tunnel junction magneto-resistive read head whose shields also function as elecrical leads to the sensing circuitry. Ishiwata (U.S. Pat. No. 5,910,870) teaches a method for forming a multi-layer magneto-resistive head structure having a laminated magnetic layer isolated from its magnetic pole layer.
Most applicable to the present invention, however, is the invention of Chen et al (U.S. Pat. No. 5,282,308), which teaches a simplified method of forming a narrow upper magnetic pole piece by joining or xe2x80x9cstitchingxe2x80x9d together two separately deposited pole pieces, the upper pole tip and the upper pole yoke, along a pedestal formed from a portion of the upper pole tip photoresist mask. In contrast to methods that form the upper pole piece and yoke monolithically, the stitching process allows the narrow tip section to be formed within a thinner photoresist mask, which is highly advantageous in the context of the fabrication process.
The present invention extends the capabilities of the stitched writer design and fabrication process by overcoming several serious deficiencies which limit its applicability to high data-rate encoding. In particular, because the stitched writer head as formed by the methods of the present art cited above has a lengthy throat region, it requires a high saturation writing current, which, in turn, causes side erasures and adversely affects data already written on adjacent disk areas. In addition, the lengthy throat region causes poor nonlinear transition shift performance (interference between the magnetic field produced by transitions already on the written medium and the field being used to write the next transitions on that medium) and poor overwrite performance (the ability to write over previously written low frequency data with new high frequency data). The present invention teaches a method for fabricating a stitched head writer than retains all the advantages of that structure and its method of fabrication, but eliminates the problems that render it less able to perform high data-rate encoding.
A first object of this invention is to fabricate a stitched pole magnetic write head that is capable of encoding magnetic data at high rates.
A second object of this invention is to fabricate a stitched pole magnetic write head that has a lower saturation write current.
A third object of this invention is to fabricate a stitched pole magnetic write head with improved nonlinear transition shift performance.
A fourth object of this invention is to fabricate a stitched pole magnetic write head having improved overwrite performance.
A fifth object of this invention is to fabricate a stitched pole magnetic write head that significantly reduces the problem of side erasure.
A sixth object of this invention is to fabricate a stitched pole magnetic write head with a reduced effective throat height.
A seventh object of this invention is to fabricate a stitched pole magnetic write head having an increased ratio of P2/P3 contact area to throat area. In this notation, P2 is the upper pole tip and P3 is the upper pole yoke piece stitched to that tip.
An eighth object of this invention is to fabricate a stitched pole magnetic write head with reduced constraints on the P2 sidewall and P3 shape.
A ninth object of this invention is to achieve each of the objects cited above without increasing the P2/P3 alignment tolerances established by the present pole stitching fabrication process.
These objects will be achieved by means of a novel modification of the present stitched pole fabrication process. The proposed modification is the formation of a non-magnetic spacer of appropriate dimension beneath the P2 portion of the upper pole assembly where it contacts the upper surface of the write gap layer. Said spacer is deposited as part of a self-aligned, patterned photoresist process, wherein the spacer is deposited first and P2 is then plated over it to form the pole tip configuration. Increasing the thickness of the spacer layer, while keeping it within a specified tolerance range, allows the upper stitched P3 portion of the pole piece to be recessed relative to the tip of P2. This stepped pole configuration allows the objects cited above to be achieved.